Primers for use with delay action blasting caps and process of blasting using the same



March 11, 1969 KE ET AL 3,431,851

E WIT PRIMERS FOR US H DEL ACTION BLASTING CAPS AND PROCESS OF BLASTUSING THE SAME Filed Aug. 1%67 Patented Mar. 11, 1969 12 Claims ABSTRACTOF THE DISCLOSURE Primer cartridges are provided adapted for use withnonelectric delay action blasting caps, initiated by low energydetonating cord, and comprising a cartridge for primer explosive, areceptacle in the cartridge for reception of a blasting cap, and atubular fuse holder means made of energy-absorbing material and attachedto the cartridge, so that the material of the fuse holder is interposedbetween the fuse and the primer cartridge wall. The tubular holderseparates the fuse from the primer wall, and prevents detonation of theprimer by the fuse.

This application is a continuation-inpart of Ser. No. 642,396, filed May31, 1967.

This invention relates to primers and to primer cartridges especiallydesigned for use with delay action blasting caps initiated by low energydetonating cord, and more particularly to primers and primer cartridgeshaving an energy-absorbing tubular fuse holder through which the fusepasses, and attached to the outside wall separating the initiating fusefor the blasting cap from the primer container wall, and to a method ofblasting using such primers, which avoids the necessity of threading orlacing the initiating fuse through the primer.

Electric blasting caps are subject to being set off by thunderstorms,stray electric currents, static electricity and RF energy, with aresulting premature explosion Consequently, for many years the explosiveindustry has been confronted with the hazards of electric blasting capsunder these conditions.

In order to overcome this problem, but still retain the delaycharacteristics of electric blasting caps, 21 nonelectrical initiatingsystem has been introduced, employing nonelectric millisecond delayblasting caps for in-hole initiation of explosives. These blasting capsprovide the precise timing of electric blasting caps, but are immune tothe hazards or effects of extraneous electricity. The system is composedof a length of low energy detonating fuse, with a delay element and anonelectric blasting cap attached to one end. The other end of thedetonating fuse is tied to a standard detonating fuse trunk line, which,when initiated, causes a detonating wave to travel down the low energydetonating fuse to the delay element. The delay element introduces apredetermined delay period, and then initiates the nonelectric blastingcap, thus duplicating the effect that would be obtained by the use of anelectric blasting cap in the same location.

In using the system with a conventional primer containing the properlyinsensitive explosive, the low energy detonating fuse is laced throughthe cartridge, and the cap inserted in the crimped end of the cartridge.Thus, the fuse actually passes through the explosive at this point, andis intimately in contact with the explosive there. It is not possible tohalf-hitch the detonating fuse around the cartridge as is usual withelectric blasting cap lit lead wires, since the fuse can cut off at thepoint of crossover.

As a consequence, the system requires that the primer used beinsensitive to initiation by the low energy detonating fuse, but it mustreadily accept detonation from a No. 6 blasting cap. Conventionalnitroglycerine-based explosives cannot be used any circumstances, sincethe fuse in most instances initiates this type of explosive, thusnullifying or short-circuiting the delay element before the cap.

This type of lacing also means that if the primer is used in awater-filled hole, Water can penetrate the explosive at the point wherethe fuse is laced through it, and depending on the type of explosive inthe primer, can migrate towards the blasting cap, reach or desensitizethe powder around the cap, and cause the primer to misfire.

Considerable private research has been carried out by the inventors inan attempt to overcome the ditliculty introduced by threading or lacingthe fuse through the cartridge. Relatively insensitive primer explosiveshave been tried in cast form, such as pentolite, composition B, andtrinitrotoluene. However, it was found that the low energy detonatingfuse when held in close contact with the cast primer, either by taping,tying, or other means, in from 25 to of the cases would rupture the castexplosive, and cause the primers to malfunction. Cardboard or papertubes were also inserted in the priming wells, but this step was equallyunsuccessful.

In accordance with the invention, a primer cartridge is provided withtubular means for holding the detonating fuse along the outside wall ofthe primer while separating it from the wall sufiiciently to avoid anydanger of detonating the primer, or of rupturing a cast primerexplosive. This tubular fuse holder means is made of energyabsorbingmaterial, and is attached to the outside wall of the primer cartridge.Through this holder is threaded the fuse running to the primer, so thatthe material of which the fuse holder is made is interposed between theprimer wall and the detonating fuse. Thus, the material separates thefuse from the primer wall, and prevents detonation of the primer by thefuse. It also eliminates the necessity of threading or lacing thedetonating fuse through the primer, in order to attach the fuse to theprimer. The tubular means for holding the detonating fuse can be firmlyattached to the cartridge, so that the fuse can be firmly atlixed to theprimer.

The primers of the invention are very easily employed in in-holeinitiation of explosives using nonelectric delay blasting caps. Thelength of low energy detonating fuse of conventional type with a delayelement and the non electric blasting cap crimped to one end is simplythreaded through the holding means for such fuse attached to the primercartridge, and the blasting cap inserted in the receptacle providedtherefor in the primer cartridge. The other end of the detonating fuseis tied to a standard detonating fuse trunk line. This, when initiated,causes the detonating wave to travel down the low energy detonating fuseto the delay element, which imparts a predetermined delay period in theusual Way, and then initiates the nonelectric blasting cap. Thedetonating wave travels safely along the low energy fuse Withoutaffecting the primer because of the insulating effect of the separatingfuse holder interposed therebetween. The result is a reliable primer foruse with delay action blasting caps of all types.

The tubular fuse holder can be made of any energyabsorbing material. Atube of rubber, either natural or synthetic, will serve. will a tube ofpaper, or synthetic resin, such as polyethylene, polypropylene,polystyrene and polyvinyl chloride. However, the wall of the tube mustbe thick enough to absorb and thus insulate the primer cartridge fromthe detonating wave traveling along the fuse to the primer. Thethickness will depend on the energy conductivity of the material; a thinlayer of a relatively high energy-absorbing material can be just aseffective as a thick layer of relatively low energy-absorbing material,and in either case the layer must be thick enough to insulate the fusefrom the container wall, and prevent the fuse from damaging the primer.It has been determined that the wall must be at least 0.005 inch thick,and preferfably it is at least 0.01 inch thick. This is somewhat thickerthan the wall of most commercially available tubes. There is no upperlimit on thickness, but a thickness greater than 0.25 inch is notnormally required.

A further insulating effect is obtained if the tubular holder is made offoamed or cellular material, which contains open cells and thus displaysan enhanced energyabsorbing and heat-insulating effectiveness. The foammaterial is preferably a foamed plastic or rubbery material, such aspolyvinyl chloride resin foam, polyurethane resin foam, foam rubber,foam nylon, foam polyethylene, and

foam polypropylene.

The tubular holder can be wide or narrow, and extends along the outsideof the primer cartridge, generally from end to end. The holder can beattached to the wall by use of any means appropriate for the purpose,such as a tape, adhesive or bonding agent.

The tube should be of a width at least equal to the diameter of thedetonating fuse, so as to insulate it fully from the cartridge wall. Itcan, if desired, be considerably wider than the detonating fuse, so asto provide an ample area for insulation protection. It is thought thatthe tube protects the primer explosive against detonation because of theinsulating effect of the tube wall, and because of its compressibility,which enables it to take up some of the shock of the detonating wavetraveling down the fuse.

Accordingly, the tube material should be compressible to a certaindegree.

The tubular holding or holder means for attaching the detonating fuse tothe cartridge can take any of several forms. A preferred embodiment is atube, such as a spiral wound cardboard tube, extending a substantialpart or all of the length of the primer cartridge. The detonating fusecan be threaded through this tube along the outside of the primercartridge.

In another embodiment, the tubular holder means takes the form of atubular channel, so shaped and sized that the fuse is tightly heldtherein in a press-fit, and is separated from the cartridge by thechannel wall. The channel can have a diameter slightly less than thediameter of the fuse, so that the fuse is slightly compressed oninsertion in the channel, and the resilient side walls of the channelare correspondingly thrust somewhat apart, due to the relativenoncompressibility of the fuse, with a corresponding spring actiontending to retain the fuse in the channel. The channel should extendover at least 180 of arc, and preferably at least 270 of are.

In still another embodiment, a channel having a plurality of loops isprovided, instead of a continuous tube, through which the fuse can bethreaded in running it to the blasting cap.

The tubular holder means can be circular, elliptical, or otherwise U- orring-shaped in cross-section.

The invention is applicable to primer cartridges of all types. Theprimer cartridge can be made of any material, such as paper, cardboard,metal or plastic, such as aluminum, steel, iron, polyvinyl chloride,polyethylene, cel lulose acetate, and ethyl cellulose.

Any primer explosive material can be packaged in the primers of theinvention, inasmuch as the explosive need not be insensitive toinitiation from the detonating fuse, due to the protection afforded bythe tubular holder. The explosive should be suificiently sensitive to bereliably initiated by a No. 6 blasting cap, but it can be more sensitivethan this, if desired. Typical primer explosives that can be employedinclude pentolite, composition B, trinitrotoluene, Cyclonite, Tetryl,special explosives and blasting agent combinations, including thenitrocarbonitrates, TNT-sensitiZed-ammonium nitrate-type slurried highexplosives, smokeless powdersensitized-ammonium nitrate-type slurriedhigh explosives, nitrostarchsensitized-ammonium nitrate-type slurriedhigh explosives, TNT-ammonium nitrate-pellet-form solid high explosives,and high explosives that include nitrostarch-sensitized-arnmoniumnitrate-type semi-solid high explosives, nitroglycerine dynamites, suchas the semi-gelatins, ammonia gelatins, and ammonia dynamites,pentaerythritol tetranitrate, and Cyclotol.

The drawings illustrate a preferred embodiment of the invention.

FIGURE 1 is a view in elevation, with parts cut away, of an explosiveprimer cartridge of the invention, showing a delay action blasting capin position in the well provided therefor.

FIGURE 2 is a cross-section taken along the lines 2--?. of the primercartridge of FIGURE 1.

FIGURE 3 shows the mode of attachment of the primer cartridge of theinvention to a detonating fuse and delay action blasting cap for in-holeinitiation.

The explosive primer of FIGURES 1 to 3 includes a primer cartridge 1made of cardboard, equipped with a blasting cap well 2 open to theatmosphere for insertion of a blasting cap 3 with a delay element as acomponent part thereof. The cartridge is filled with a high explosive 4,such as pentolite, in cast or powdered form.

Attached to one side of the cartridge, and extending from end to end ofthe cartridge, is a polyethylene tube 6, wall thickness 0.04 inch,internal diameter 5 inch, 21 diameter sufficient to receive a detonatingfuse 7 running to the blasting cap 3. This tube is attached to thecartridge by a suitable adhesive 5.

If desired, on top of the charge of primer high explosive or blastingagent combination there can be placed a booster cup containing a boosterexplosive. Any booster explosive can be used, preferably in cast form,such as pcntolite or composition B. If used, the detonating velocity ofthe booster explosive is sufficient to initiate the primer. This boostercup is also sealed in the explosive cartridge, and the blasting cap wellis inserted in the booster cup for initiation of the booster.

In practice, as shown in FIGURE 3, a length of low energy detonatingfuse 7, with a delay element-fitted nonelectric blasting cap 3 crimpedto one end, is threaded through the tube 6, while the blasting cap isinserted in the well 2. The other end of the detonating fuse is tied viasuitable connector 8, such as a J-connector, to a standard detonatingfuse trunk line 10, to which can be afiixed a plurality of such primerassemblies (not shown) with blasting cap attached. The primer is thenslipped into a bore hole 12.

When the detonating fuse trunk line 10 is initiated, the detonating wavetravels down it, and then down each of the low energy detonating fuses 7attached thereto, running to the delay element through the tube 6without affecting the primer. The delay element imparts a predetermineddelay period, and then initiates the blasting cap, setting off theprimer.

A number of primers were prepared, of the type shown in FIGURES 1 to 3,utilizing fuse holder tubes 6 of a variety of materials. These weretested to deter-mine resistance of the primer to damage by the fuse. ThePrimaline PETN detonating fuse was used. A tube of plastic straw(polyvinyl chloride) wall thickness 0.008 inch, I.D. Q4 inch wascompared with a Kraft paper tube, 0.012 inch wall thickness, I.D. inchand with a polyethylene tube, airline type, 0.04 inch wall thickness, LDinch. In the test, each was afiixed to the canister wall of a /3 lb.cast pentolite primer. The Primaline was then threaded through the tube.All three materials prevented the wall of the canister from beingruptured when the Primaline detonated. When the Primaline was afiixed tothe wall of the primer canister without the benefit of the tubularinsulator, the wall was torn, and the pentolite fractured and partiallydisplaced from the area adjacent to the Primaline.

These data show the effectiveness of the insulating tube in preventingprimer damage.

The water-resistance of the primers in accordance with the invention isgreatly enhanced, because the detonating fuse is not laced or threadedthrough it. Consequently, the primers can be employed in water-filledholes without introducing any problem. All that is necessary is that theprimer cartridge itself be water-proof, or sufficiently water resistantso that water does not have time to penetrate to and desensitize theprimer before the charge is set off. The primer is sufficientlyversatile to permit its use in nonelectrical delay initiation systems ofconventional type, employing the usual types of fuse delay elements fornonelectric blasting caps.

Having regard to the foregoing disclosure, the following is claimed asthe inventive and patentable embodiments thereof:

1. A primer cartridge especially adapted for use with nonelectric delayaction blasting caps and detonating fuse, comprising a cartridge for aprimer explosive having means permitting insertion of a blasting cap injuxtaposition to the primary explosive; and a tubular fuse holder meansof energy absorbing material on the exterior of the cartridge forguiding a detonating fuse to the blasting cap, said fuse holder having awall attached to the exterior cartridge wall and interposed between thedctonating fuse therein and the cartridge so as to protect the cartridgefrom rupture and inhibit premature detonation of the explosive in thecartridge by a detonating wave along the detonating fuse to the blastingcap, thereby ensuring that the explosive in the cartridge is detonatedonly after the delay introduced by the blasting cap.

2. A primer cartridge in accordance with claim 1, n which the holdermeans is a tube having a diameter slightly larger than the diameter ofthe detonating fuse.

3. A primer cartridge in accordance with claim 1, in which the holdermeans is a channel extending over at least 180 of are.

4. A primer cartridge in accordance with claim 1, in which theenergy-absorbing material of which the tube i formed is a plasticmaterial.

5. A primer cartridge in accordance with claim 4, in which the plasticmaterial is a plastic foam.

6. A primer cartridge in accordance with claim 1, in which the wall ofthe tube is at least 0.005 inch thick.

7. A primer comprising a primer cartridge in accord-v ance with claim 1,filled with a primer explosive.

8. A primer in accordance with claim 7, in which the explosive is incast form.

9. A primer in accordance with claim 7, in which the explosive is inpowdered form.

10. In the process for blasting using a nonelectric delay actionblasting cap, detonating fuse, and a primer ex plosive in a primercartridge in which after initiation of the detonating fuse, whichinitiates the blasting cap, a predetermined delay occurs before theprimer explosive in the cartridge is detonated, the improvement whichcom prises guiding the fuse to the blasting cap along the exterior ofthe cartridge in a tubular fuse holder of energy absorbing material witha wall of the holder interposed between the fuse and the cartridge toabsorb the force of the detonating wave while the detonating wave istravelling along the fuse to the blasting cap to thereby prevent ruptureof the cartridge, and, inhibit premature detonation of the primerexplosive but permit the blasting cap to be detonated.

11. The process according to claim 10, in which the absorbing layer is aplastic material.

12. The process according to claim 1], in which the plastic material isa polyethylene.

References Cited UNITED STATES PATENTS 1,512,714 10/1924 Saucier 102242,708,408 5/1955 Sweetman 1022O 3,129,663 4/1964 Schnepfe 102-273,311,056 3/1967 Noddin 102-27 VERLIN R. PEND-EGRASS, Prinmry Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,431,851 March 11, 1969 Forest L. Kern et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, lines 6 to 8, "assignors toTrojan Powder Company, Allentown, Pa. a corporation of Pennsylvaniashould read assignors, by mesne assignments, to Commercial SolventsCorporation, a corporation of Maryland Signed and sealed this 17th dayof March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

